I think that if you are going to spend all this time and money on spray insulation in the ceiling you might as well pull the entire roof off the trailer and go all the way. This way you can get rid of any water damaged wood and install all the ceiling panels properly giving a factory look. Insulating will be a breeze from the top. You can also get rid of the problematic metal roof (maybe get a few $$ for the scrap metal) and install new EPDM or maybe rhinoline it....
OK enough sarcasm... just repair what needs repairing without going overboard, and go have fun in it... That is what RVing is all about..
